Apparatus and method for reducing power consumption of receiving data in wireless communication system

ABSTRACT

A wireless communication method of a receiver, including performing a first determination of whether to decode a control channel of a current time transmission interval (TTI) based on control channel information of a previous TTI; decoding the control channel of the current TTI based on a result of the first determination; performing a second determination of whether a data channel is included in the current TTI based on a result of the decoding; and performing a third determination of whether to deactivate a communication interface configured to process a received signal based on a result of the second determination

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation of U.S. application Ser. No. 17/204,038 filedMar. 17, 2021, which is based on and claims priority under 35 U.S.C. §119 to Korean Patent Application No. 10-2020-0073729, filed on Jun. 17,2020, in the Korean Intellectual Property Office, the disclosure ofwhich is incorporated by reference herein in its entirety.

BACKGROUND 1. Field

The disclosure relates to an apparatus and method for reducing powerconsumption of receiving data in wireless communication system.

2. Description of Related Art

In order to meet the increasing demand for wireless data traffic sincethe commercialization of 4th generation (4G) communication systems,efforts have been made to develop an improved 5G communication system,and accordingly, a 5G communication system has recently beencommercialized.

Consideration is being given to implementing the 5G communication systemin millimeter wave (mmW) frequency bands (e.g., 60 GHz bands) toaccomplish higher data rates. In order to mitigate propagation loss andincrease the propagation distance, discussions are underway aboutvarious techniques, such as beamforming, massive multiple-input multipleoutput (MIMO), full dimensional MIMO (FD-MIMO), array antenna, analogbeamforming, and large-scale antenna in the 5G communication system.

Also, in order to enhance the network performance of the 5Gcommunication system, developments are underway about varioustechniques, such as evolved small cell, advanced small cell, cloud radioaccess network (RAN), ultra-dense network, device-to-device (D2D)communication, wireless backhaul, moving network, cooperativecommunication, coordinated multi-points (CoMP), and interferencecancellation.

Furthermore, the ongoing research includes the use of hybrid frequencyshift keying and quadrature amplitude modulation (FQAM) and slidingwindow superposition coding (SWSC) as advanced coding modulation (ACM),and filter bank multi-carrier (FBMC), non-orthogonal multiple access(NOMA), and sparse code multiple access (SCMA) as advanced accesstechniques.

As a result of the commercialization of 5G following 4G, the data ratesupported by a wireless communication system has rapidly increased, andhigh-definition/large-capacity multimedia services may be supported by awireless communication terminal. Accordingly, the power efficiency ofthe wireless communication device has become more important.

In such a wireless communication system, in order for a terminal tosuccessfully receive data transmitted from a base station or anotherterminal, accurate information about a wireless channel between atransmitter, for example a base station or a terminal, and a receiver,for example another terminal may be beneficial. Furthermore, in order toestimate the wireless channel, the transmitter transmits a predefinedreference signal, and the receiver estimates the wireless channel basedon the received reference signal. For example, in the 4G and 5Gcommunication systems, the reference signal for data reception, forexample a Cell-Specific Reference Signal (CRS) in 4G, DemodulationReference Signal (DRS) in 5G, may be transmitted from the transmitter tothe receiver every transmission time interval (TTI), for example asub-frame of 4G or slot of 5G.

As described above, the wireless communication system may performreference signal-based wireless channel estimation for data reception.The reference signal for channel estimation is transmitted every timeunit, for example every TTI, and the terminal may perform channelestimation every time unit in order to optimize reception performance.However, when a wireless channel characteristic hardly changes for acertain period of time, for example when the coherence time for whichthe wireless channel characteristic is maintained is long, it may be awaste of power for the terminal to perform a channel estimationoperation every time unit.

In addition, in a case where data is transmitted sparsely, such as voiceover Long-Term Evolution (LTE) (VoLTE), a control channel may becontinuously monitored to check whether data has been transmitted. Inthis case, there may be a problem in that the power required tocontinuously monitor the control channel occupies a significant portionof the total power consumption of the terminal.

SUMMARY

Provided are an apparatus and method for efficiently reducing powerconsumption when a wireless communication system receives data.

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of the presented embodiments.

In accordance with an aspect of the disclosure, a wireless communicationmethod of a receiver includes performing a first determination ofwhether to decode a control channel of a current transmission timeinterval (TTI) based on control channel information of a previous TTI;decoding the control channel of the current TTI based on a result of thefirst determination; performing a second determination of whether a datachannel is included in the current TTI based on a result of thedecoding; and performing a third determination of whether to deactivatea communication interface configured to process a received signal basedon a result of the second determination.

In accordance with an aspect of the disclosure, a receiver includes acommunication interface configured to process a signal received from atransmitter; and a controller configured to control the communicationinterface, wherein the controller is further configured to: control thecommunication interface to decode a control channel of a currenttransmission time interval (TTI) after determining whether to decode thecontrol channel of the current TTI based on control channel informationof a previous TTI; and determine whether to deactivate the communicationinterface after determining whether a data channel is included in thecurrent TTI based on a decoding result.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainembodiments of the present disclosure will be more clearly understoodfrom the following detailed description taken in conjunction with theaccompanying drawings in which:

FIG. 1 is a diagram illustrating a wireless communication systemaccording to an embodiment;

FIG. 2 is a block diagram illustrating a receiver of FIG. 1 , accordingto an embodiment;

FIG. 3 is a block diagram illustrating a communication unit of FIG. 2 ,according to an embodiment;

FIG. 4 is a diagram illustrating a channel adaptive power control modeimplemented by the receiver of FIG. 1 , according to an embodiment;

FIG. 5 is a timing diagram illustrating an example of a channel decodingmethod of the receiver of FIG. 1 , according to an embodiment;

FIG. 6 is a timing diagram illustrating another example of a channeldecoding method of the receiver of FIG. 1 , according to an embodiment;

FIG. 7 is a flowchart illustrating an example of a wirelesscommunication method of the receiver of FIG. 1 , according to anembodiment;

FIG. 8 is a flowchart illustrating an example of S100 in FIG. 7 ,according to an embodiment;

FIG. 9 is a flowchart illustrating an example of S400 of FIG. 7 ,according to an embodiment;

FIG. 10 is a flowchart illustrating an example of S415 of FIG. 9 ,according to an embodiment;

FIG. 11 is a flowchart illustrating an example of a wirelesscommunication method of the receiver of FIG. 1 , according to anembodiment; and

FIG. 12 is a flowchart illustrating an example of a wirelesscommunication method of the receiver of FIG. 1 , according to anembodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments will be described in detail with reference tothe accompanying drawings.

Advantages and features and methods to achieve the same are describedmore fully hereinafter with reference to the accompanying drawings inwhich embodiments are shown.

The disclosure may, however, be embodied in many different forms andshould not be construed as limited to the embodiments set forth herein.Rather, these embodiments are provided so that this disclosure isthorough, and will fully convey the scope to those skilled in the art.Specific configurations described only in each embodiment may be used inother embodiments. Like reference numerals refer to like componentsthroughout the present specification.

Terms used herein are for describing the embodiments and are notintended to limit the disclosure. In the present specification, asingular expression includes a plural expression unless the contextclearly indicates otherwise. It will be further understood that theterms “comprises” and/or “comprising”, when used in this specification,specify the presence of stated features, steps, operations and/orcomponents do not preclude the presence or addition of one or morefeatures, steps, operations and/or components.

Unless otherwise defined, all terms including technical and scientificterms used herein have the same meaning as commonly understood by one ofordinary skill in the art to which the disclosure pertains. Terms, suchas those defined in commonly used dictionaries, are not to be construedin an idealized or overly formal sense unless expressly so definedherein.

In describing embodiments in detail, although the embodiments may relateto a new radio (NR) system and a long term evolution (LTE)/LTE-advanced(LTE-A) system, it is to be understood that the subject matter to beclaimed herein may be applied to other communication systems havingsimilar technical backgrounds as well as other communication systemsusing licensed and unlicensed bands without departing from the scope ofthe disclosure herein, and this will be possible at the discretion ofthe person skilled in the art.

Before undertaking the detailed description below, it may beadvantageous to set forth definitions of certain words and phrases usedthroughout this patent document. The term “connect or couple” and itsderivatives refer to any direct or indirect communication between two ormore components, whether or not those components are in physical contactwith one another. The term “transmit,” “receive,” and “communicate,” aswell as derivatives thereof, encompass both direct and indirectcommunication. The term “include” and “comprise,” as well as derivativesthereof, mean inclusion without limitation. The term “or” is inclusive,meaning and/or. The phrase “associated with,” as well as derivativesthereof, means to include, be included within, interconnect with,contain, be contained within, connect to or with, couple to or with, becommunicable with, cooperate with, interleave, juxtapose, be proximateto, be bound to or with, have, have a property of, have a relationshipto or with, or the like. The term “controller” means any device, systemor part thereof that controls at least one operation. Such a controllermay be implemented in hardware or a combination of hardware and softwareand/or firmware. The functionality associated with any particularcontroller may be centralized or distributed, whether locally orremotely. The phrase “at least one of,” when used with a list of items,means that different combinations of one or more of the listed items maybe used, and only one item in the list may be needed. For example, “atleast one of: A, B, and C” includes any of the following combinations:A, B, C, A and B, A and C, B and C, and A and B and C.

Moreover, various functions described below may be implemented orsupported by one or more computer programs, each of which is formed fromcomputer-readable program code and embodied in a computer-readablerecording medium. The terms “application” and “program” refer to one ormore computer programs, software components, sets of instructions,procedures, functions, objects, classes, instances, related data, or aportion thereof adapted for implementation in a suitablecomputer-readable program code. The phrase “computer-readable programcode” includes any type of computer code, including source code, objectcode, and executable code. The phrase “computer-readable recordingmedium” includes any type of medium capable of being accessed by acomputer, such as read only memory (ROM), random access memory (RAM), ahard disk drive, a compact disc (CD), a digital video disc (DVD), or anyother type of memory. A “non-transitory” computer-readable recordingmedium excludes wired, wireless, optical, or other communication linksthat transport transitory electrical or other signals. A non-transitorycomputer-readable recording medium includes media where data may bepermanently stored and media where data may be stored and lateroverwritten, such as a rewritable optical disc or an erasable memorydevice.

Hereinafter, various embodiments of the disclosure will be describedbased on an approach of hardware. However, various embodiments of thedisclosure include a technology that uses both hardware and software andthus, the various embodiments of the disclosure may not exclude theperspective of software.

In addition, terms referring to control information, terms referring toan entry, terms referring to network entities, terms referring tomessages, terms referring to components of devices, etc. are used forconvenience of explanation. Accordingly, the disclosure is not limitedto terms to be described later, and other terms having an equivalenttechnical meaning may be used.

FIG. 1 is a diagram illustrating a wireless communication system 100according to an embodiment.

Referring to FIG. 1 , the wireless communication system 100 may includea transmitter 110 and a receiver 120.

For reference, although the transmitter 110 and the receiver 120 aredepicted as separate entities in FIG. 1 , the transmitter 110 and thereceiver 120 may include transmitting and receiving ends capable ofperforming both transmission and reception operations, respectively. Inaddition, in FIG. 1 , the wireless communication system 100 is depictedas including only one transmitter 110 and one receiver 120, but inembodiments the wireless communication system 100 may includetransmitters and receivers.

The transmitter 110 and the receiver 120 of FIG. 1 refer to devicescapable of transmitting or receiving signals over a wireless network.

Specifically, the transmitter 110 and the receiver 120 may be referredto by terms such as a mobile station, user equipment, a subscriberstation, a user terminal, a remote terminal, and a wireless terminal. Inaddition, the transmitter 110 and the receiver 120 may be referred to byterms such as a base station, an evolved Node B (eNB), a next generationNode B (gNB), and an access point (AP). Further, each of the transmitter110 and the receiver 120 may be a mobile device such as a mobile phoneor a smart phone, or a stationary device such as a desktop computer.

In embodiments, a protocol applied to the wireless communication system100 of FIG. 1 may include cellular communication such as LTE (long termevolution), LTE-A (LTE-Advanced), NR (New Radio), WiBro (WirelessBroadband), and GSM (Global System for Mobile Communication), and mayinclude short-range communication such as Wireless Fidelity (WiFi),Bluetooth, and Near Field Communication (NFC).

In addition, the transmitter 110 and the receiver 120 of FIG. 1 maytransmit or receive signals using an orthogonal frequency divisionmultiplexing (OFDM) scheme in a multiplexing scheme. In addition, thetransmitter 110 and the receiver 120 may transmit or receive signalsusing code division multiple access (CDMA), frequency division multipleaccess (FDMA), or time division multiple access (TDMA).

In addition, the transmitter 110 and the receiver 120 of FIG. 1 mayinclude a single antenna or a plurality of antennas, and accordingly,transmission or reception techniques such as multiple-inputmultiple-output (MIMO), multiple-input single-output (MISO),single-input multiple-output (SIMO), or single-input single-output(SISO) may be applied.

In addition, the wireless channel of FIG. 1 is a path through whichsignals are transmitted or received. In the wireless channel, signalsmay be scattered, reflected, and refracted by a scatterer, reflector,etc. and delayed in a time domain or transmitted through multiple paths.Due to the Doppler effect caused by the movement of the transmitter 110or the receiver 120, a Doppler shift phenomenon in which the frequencyof the signal received by the receiver 120 is different from thefrequency of the signal transmitted by the transmitter 110 may occur.Also, a channel that rapidly changes over time as described above may bereferred to as a fast fading channel.

For reference, various embodiments provide a method of selectivelyperforming channel estimation on a channel that changes rapidly or doesnot change over time.

FIG. 2 is a block diagram illustrating the receiver 120 of FIG. 1 ,according to an embodiment.

A term such as ‘unit’ and ‘part’ used herein indicates a unit forprocessing at least one function or operation and may be implementedusing hardware, software, or a combination of hardware and software.

Referring to FIG. 2 , the receiver 120 may include a communication unit210, a controller 220, and a storage 230.

The communication unit 210 may perform functions for transmitting andreceiving signals through a wireless channel. That is, the communicationunit 210 may process a signal received from the transmitter 110. Forexample, the communication unit 210 may perform reception of a radiofrequency (RF) signal, conversion of frequency, demodulation, decoding,removing of a cyclic prefix (CP), and Fast Fourier transform (FFT),channel estimation, equalization, etc.

The controller 220 controls overall operations of the receiver 120. Forexample, the controller 220 may receive a signal transmitted from thetransmitter 110 through the communication unit 210 and control thecommunication unit 210. In addition, the controller 220 may write orread data in or from the storage 230. To this end, the controller 220may include at least one processor, a microprocessor, or amicrocontroller, or may be a part of a processor.

The storage 230 may store data such as a base program, an applicationprogram, and setting information for the operation of the receiver 120.For example, the storage 230 may perform functions for storing dataprocessed by the controller 220. Accordingly, the storage 230 may storecontrol channel information or data channel information, channelcharacteristic maintenance time information, etc. of a previous TTI.Also, the storage 230 may include a volatile memory, a nonvolatilememory, or a combination of a volatile memory and a nonvolatile memory.For example, the storage 230 may include RAM, flash memory, etc.

In FIG. 2 , the receiver 120 includes the communication unit 210, thecontroller 220, and the storage 230. Two or more of the communicationunit 210, the controller 220, and the storage 230 may be integrated intoone, and the receiver 120 may further include an additional component inaddition to the above-described component. However, for convenience ofdescription, the receiver 120 including the above-described componentswill be described as an example.

FIG. 3 is a block diagram illustrating the communication unit 210 ofFIG. 2 , according to an embodiment.

Referring to FIG. 3 , the communication unit 210 may include a radiofrequency (RF) processing unit 214 that converts an RF signal, forexample a high frequency band signal, into a baseband signal, forexample a low frequency band signal, and a baseband processing unit 218that processes the baseband signal.

Specifically, the RF processing unit 214 may include a Front End Module(FED) and a Radio Frequency IC (RFIC). In addition, the FED and the RFICmay include at least one of a phase locked loop (PLL), a voltage controloscillator (VCO), a low noise amplifier (LNA), a mixer, a localoscillator (LO), and an analog-to-digital converter (ADC).

In addition, the baseband processing unit 218 may include at least oneof an RX filter, an automatic gain controller (AGC), an automaticfrequency controller (AFC), a timing synchronizer (TS), a channelestimator, a demodulator, and a decoder.

Here, the RX filter may filter only frequency signals that may bereceived and processed by the terminal from among downlink signalsreceived from antenna ports of a base station through a wirelesschannel. The RX filter may also convert the received signals intodigital signals. That is, an ADC may be included in the RX filter.

An AGC may control a gain to maintain the magnitude of the receivedsignal at an appropriate level, and an AFC may obtain frequencysynchronization of the received signal.

In addition, a TS may obtain time synchronization of the receivedsignal, and a channel estimator may estimate the channel value withrespect to each resource element based on a reference signal receivedfrom the base station.

In addition, the demodulator may detect a data signal based on theestimated channel value and the received signal and demodulate thedetected value. Here, the operation of detecting the data signal mayinclude an operation of obtaining the data signal estimated by using achannel value, for example the estimated channel value, corresponding tothe resource element, for example a resource element to which the datasignal is mapped.

The decoder may obtain a data signal intended to be transmitted from thebase station to the terminal by descrambling and decoding thedemodulated data signal.

For reference, depending on the situation, for example when the channelinformation of a previous TTI is reused for a channel decoding operationof a current TTI, the channel estimation operation of the channelestimator may be skipped in the baseband processing unit 218.

Further, the communication unit 210 may further include components otherthan the components illustrated in FIG. 3 or may not include some of thecomponents illustrated in FIG. 3 . For convenience of explanation, thecommunication unit 210 including the components shown in FIG. 3 will bedescribed as an example.

As described above, the communication unit 210 may include theabove-described components, and the operation of each component may becontrolled by the controller 220.

In embodiments, the receiver 120 may operate in a channel adaptive powercontrol mode in order to reduce power consumed when receiving data. Inthis case, the controller 220 may individually control each component ofthe communication unit 210.

A more detailed description of the channel adaptive power control modeof the receiver 120 will be described later.

For reference, a signal reception operation of the receiver 120according to an embodiment will be described as follows.

Specifically, in the wireless communication system 100 according to anembodiment, the receiver 120; for example, a user terminal, may decode acontrol channel, for example a downlink control channel, transmittedfrom the transmitter 110; for example, the base station, every TTI toobtain various information, for example downlink data grant, downlinkdata format, uplink data grant, uplink data format, uplink powercontrol, etc. When a decoding operation is completed, the receiver 120may determine whether there is a data channel, for example a downlinkdata channel, in the corresponding TTI, for example TTI1, based on thepresence or absence of the downlink data grant.

When there is not a data channel in the corresponding TTI, the receiver120 may turn off the power of the communication unit 210 until a nextTTI, for example TTI2, starts in order to save power. That is, when thecontroller 220 obtains information that there is not a downlink datagrant, the controller 220 may turn off each component in thecommunication unit 210 as soon as possible. For reference, an interval,for example t3-t4 and t5-t6 in FIG. 5 , in which the power of thecommunication unit 210 may be turned off is referred to as a powercontrollable interval.

In the case of a unit requiring a stabilization time after turn-on, suchas the RF processing unit 214 in the communication unit 210, consideringthe stabilization time, the unit may be turned on by the controller 220before a next TTI, for example TTI2, starts to prepare for reception ofa signal from the transmitter 110 in FIG. 1 .

In embodiments, turning off a unit, device, or other component may bereferred to as deactivating the unit, device, or other component, andturning on a unit, device, or other component may be referred to asactivating the unit, device, or other component.

Further, in the embodiment, when the channel characteristic in theprevious TTI is maintained in the current TTI, a channel estimationvalue with respect to the control channel or the data channel obtainedin the previous TTI, or another value, for example a signal-to-noiseratio (SNR) and noise plus interference variance (NIV) estimation value,a Doppler estimation value, a delay spread estimation value, and aninterference whitening (IW) filter, may be reused even in the currentTTI such that the decoding time with respect to the control channel ordata channel may be shortened in the current TTI.

That is, when the channel characteristic in the previous TTI ismaintained even in the current TTI, the decoding operation on thecontrol channel may be completed earlier compared to a related artmethod because there is no need to perform the channel estimationoperation on the control channel in the current TTI. Furthermore, whenit is determined that there is not a data channel in the current TTI asa result of decoding the control channel, the controller 220 may turnoff each component in the communication unit 210 faster by the timerequired for various estimation and filter generation tasks required forchannel decoding, thereby reducing power consumption when receivingdata.

For reference, the channel characteristic may refer to variouschannel-related characteristics such as the number of reflected waves ona signal path, a phase of the reflected waves, a time delay, signalpower, etc.

As such, the signal reception operation of the receiver 120 may beperformed as described above. Hereinafter, examples of the channeladaptive power control mode operation of the receiver 120 will bedescribed in detail with reference to FIGS. 4 to 6 .

For reference, FIGS. 4 to 6 will be described together with reference toFIGS. 1 to 3 .

Referring to FIG. 4 , a channel adaptive power control mode operation ofthe receiver 120 is illustrated.

Specifically, when the receiver 120 operates in a channel adaptive powercontrol mode, the controller 220 may selectively turn off each componentof the communication unit 210 in the above-described situation whenpower saving is possible.

Specifically, the controller 220 may determine whether to decode acontrol channel of a current TTI based on control channel information ofa previous TTI, and control the communication unit 210 to decode acontrol channel of the current TTI based on a determination result.Also, the controller 220 may determine whether there is a data channelin the current TTI based on a decoding result, and determine whether toturn off the communication unit 210 based on the determination result.

Here, when it is determined that the data channel is not in the currentTTI, the controller 220 may turn off some components of thecommunication unit 210, switch some other components of thecommunication unit 210 to a standby state or a sleep state, and maintainthe remaining components of the communication unit 210 in an always onstate.

In order to receive a new signal from the transmitter 110 in a TTI thatimmediately follows the current TTI, the controller 220 may, immediatelybefore the current TTI ends, turn on some components of thecommunication unit 210 which have been turned off, and reactivate someother components of the communication unit 210 that have switched to thestandby state or the sleep state.

For reference, in the case of the components of the RF processing unit214 such as PLL, VCO, LNA, mixer, LO, ADC, etc. a switching time and aninternal initial value considering a warm-up time may be different foreach component. Here, the internal initial value may mean an arbitraryinitial value that is set when power is turned off and then turned on.For example, in the case of the PLL, when power is turned off and thenturned on, an initial phase value may be set to an arbitrary value.

That is, hardware components for signal reception may have differentswitching times and internal initial values. Therefore, in order tomaximize the power saving effect, the switching time, the time tonormalize the internal initial value, etc., may be compared with thepower controllable interval, for example power controllable intervals 1and 2 in FIG. 5 , to individually control the power of each component orseparately control the power of components having the similar switchingtime.

In this case, a control interface of the controller 220 with respect tothe baseband processing unit 218 and the RF processing unit 214 may beimplemented for each component or component group according to the powercontrol frequency. That is, the control interface by the controller 220may be defined differently according to the power control timingrequirement.

In addition, a power control scheme with respect to each component oreach component group, represented in FIG. 4 as, for example, powercontrol 0 through power control N and always on, may include not onlysimple power turn-off but also switching to the standby state, the sleepstate, etc. Some components or component groups may be maintained in analways on state.

That is, a control scheme in the channel adaptive power control mode maybe defined as turn on/turn off, standby state switching, sleep stateswitching, always on, etc. based on state switching time, on/off timing,internal initial value, etc. of each component or each component group.Accordingly, when the power controllable interval arrives, somecomponents may be turned off, some components are switched to thestandby state or the sleep state, and some components may be maintainedin the on state.

Otherwise, when it is determined that there is the data channel in thecurrent TTI, the controller 220 may maintain the communication unit 210in the on state. Further, the controller 220 may determine whether todecode the data channel of the current TTI based on the data channelinformation of the previous TTI, and control the communication unit 210to decode the data channel of the current TTI based on a determinationresult.

For reference, the data channel information may include at least one ofa channel estimation value related to the data channel, an SNR and NIVestimation value, a Doppler estimation value, a delay spread estimationvalue, and an IW filter. In addition, the control channel informationmay include a channel estimation value related to the control channel,an SNR and NIV estimation value, a Doppler estimation value, a delayspread estimation value, and an IW filter.

For example, in an embodiment, the data channel information maybasically include the channel estimation value related to the datachannel, and may or may not include other values depending on thesituation. Also, the control channel information may basically includethe channel estimation value related to the control channel, and may ormay not include other values depending on the situation. The disclosureis not limited thereto.

In summary, the controller 220 may control power consumption of thecomponents in the RF processing unit 214 and the baseband processingunit 218 using information about whether there is a data channelobtained through control channel decoding for each TTI. That is, thecontroller 220 may check whether there is a data channel through controlchannel decoding in each TTI, and, based on a check result, control thepower consumption of each component individually or in groups accordingto characteristics of the components in the RF processing unit 214 andthe baseband processing unit 218. The components in the RF processingunit 214 and the baseband processing unit 218 may be controlled by thecontroller 220 in a manner that minimizes performance loss andprocessing time.

Here, referring to FIGS. 5 and 6 , a channel decoding method of thereceiver 120 driven in the above-described channel adaptive powercontrol mode is illustrated, according to embodiments.

First, referring to FIG. 5 , a first TTI TTI1 and a second TTI TTI2 areshown, and an operation of estimating the control channel may beperformed during t1 to t2 of the first TTI TTI1. In addition, thecontrol channel decoding operation may be performed during t2 to t3based on the control channel estimation value, and whether there is adata channel at the first TTI TTI1 may be checked through thecorresponding decoding operation.

In addition, when it is determined that there is not a data channel as aresult of the decoding operation, t3 to t4 becomes a power controllableinterval 1, and thus, the controller 220 may control the powerconsumption of the components in the RF processing unit 214 and thebaseband processing unit 218.

Further, when the channel characteristic between the first TTI TTI1 andthe second TTI TTI2 is maintained, the control channel may be decodedduring t4 to t5 of the second TTI TTI2 based on the control channelestimation value from the first TTI TTI1. That is, the control channelestimation value from the first TTI TTI1 is reused in the second TTITTI2.

In addition, as a result of the decoding operation, when it isdetermined that there is not a data channel, t5 to t6 becomes a powercontrollable interval 2, and thus, the controller 220 may control thepower consumption of the components in the RF processing unit 214 andthe baseband processing unit 218.

Because the channel estimation operation of decoding a separate controlchannel is not performed in the second TTI TTI2, the power controllableinterval 2 of the second TTI TTI2 is longer than the power controllableinterval 1 of the first TTI TTI1.

Accordingly, the power consumption in the second TTI TTI2 may be reducedcompared to the related art.

Next, referring to FIG. 6 , the first TTI TTI1 and the second TTI TTI2are shown, according to an embodiment, and an operation of estimatingthe control channel may be performed during t1 to t2 of the first TTITTI1. In addition, the control channel decoding operation may beperformed during t2 to t3 based on the control channel estimation value,and whether there is a data channel from the first TTI TTI1 may bechecked through the corresponding decoding operation.

In addition, when it is determined that there is a data channel as aresult of the decoding operation, an operation of estimating the datachannel may be performed during t3 to t4. In addition, the data channeldecoding operation may be performed during t4 to t5 based on the datachannel estimation value, and the data signal may be obtained at thefirst TTI TTI1 through the corresponding decoding operation.

Further, when the channel characteristic between the first transmissiontime interval TTI1 and the second transmission time interval TTI2 ismaintained, the control channel may be decoded during t5 to t6 of thesecond TTI TTI2 based on the control channel estimation value from thefirst TTI TTI1. That is, the control channel estimation value in thefirst TTI TTI1 is reused in the second TTI TTI2.

In addition, when it is determined that there is a data channel as aresult of the decoding operation, the data channel may be decoded duringt6 to t7 of the second TTI TTI2 based on the data channel estimationvalue from the first TTI TTI1. That is, the data channel estimationvalue in the first TTI TTI1 is reused in the second TTI TTI2.

In this case, because the channel estimation operation for separate datachannel decoding and control channel decoding is not performed in thesecond TTI TTI2, power required for performing the corresponding channelestimation operation may be saved.

As described above, in an embodiment, the channel decoding operation isperformed by the receiver 120 by using the above-described method inorder to reduce power consumed when receiving data. Hereinafter, withreference to FIGS. 7 to 10 , an example of a wireless communicationmethod (i.e., a channel decoding method) of the receiver 120 of FIG. 1will be described in detail.

FIG. 7 is a flowchart illustrating an example of a wirelesscommunication method of the receiver 120 of FIG. 1 . FIG. 8 is aflowchart specifically illustrating an example of operation S100 in FIG.7 . FIG. 9 is a flowchart specifically illustrating an example ofoperation S400 of FIG. 7 . FIG. 10 is a flowchart specificallyillustrating an example of operation S415 of FIG. 9 .

For reference, FIGS. 7 to 10 will be described together with referenceto FIGS. 1 to 3 .

Referring to FIG. 7 , first at operation S100, it is determined whetherto decode a control channel of a current TTI based on control channelinformation of a previous TTI.

Specifically, the controller 220 may determine whether to decode acontrol channel of a current TTI based on control channel information ofa previous TTI. Here, the control channel information of the previousTTI may be stored in the storage 230, and the controller 220 mayretrieve and use the control channel information of the previous TTI,stored in the storage 230, through a read operation as necessary.

Operation S100 of determining whether to decode a control channel of acurrent TTI based on control channel information of a previous TTI mayinclude operation S105 of checking whether a channel characteristicmaintenance time has ended and operations S107 to S135 of determiningwhether to reuse the control channel information of the previous TTIbased on a check result of operation S105.

That is, when the current TTI starts, the controller 220 may checkwhether the channel characteristic maintenance time has ended, anddetermine whether to reuse the control channel information of theprevious TTI in the current TTI based on a check result.

For reference, when it is determined that channel characteristic betweenadjacent TTIs (e.g., an n TTI and an n+1 TTI) is maintained, the channelcharacteristic maintenance time may mean a period during which channelinformation of a specific TTI is reused for a certain period, that is, aperiod during which channel information of a specific TTI is reused froma next TTI (e.g. an n+2 TTI) to a certain TTI (e.g. an n+9 TTI).

The definition and duration of the channel characteristic maintenancetime may vary according to a method of determining whether to maintainthe channel characteristic or who a user or manufacturer is.

Here, referring to FIG. 8 , an example of a specific process ofoperation S100 is shown, according to an embodiment.

Operation S100 of determining whether to decode a control channel of acurrent TTI based on control channel information of a previous TTI maystart with operation S105 of determining whether the channelcharacteristic maintenance time has ended.

Specifically, when it is determined that the channel characteristicmaintenance time has not ended in operation S105, the control channelinformation of the previous TTI may be reused for the control channeldecoding of the current TTI in operation S107.

That is, when the channel characteristic maintenance time has not ended,the controller 220 may control the communication unit 210 to reuse thecontrol channel information of the previous TTI stored in the storage230 and to decode the control channel of the current TTI.

Otherwise, when it is determined that the channel characteristicmaintenance time has ended in operation S105, the control channelinformation of the previous TTI is not reused for the control channeldecoding of the current TTI, and control channel information differentfrom the control channel information of the previous TTI may be used forthe control channel decoding of the current TTI.

Specifically, when it is determined in operation S110 that the currentTTI is a TTI immediately after the channel characteristic maintenancetime has ended, the different control channel information may includecontrol channel information newly obtained from the current TTI. In thiscase, the control channel information newly obtained from the currentTTI for example control channel information of the current TTI, may beused for control channel decoding of the current TTI in operation S112.

That is, when the current TTI is the TTI immediately after the channelcharacteristic maintenance time has ended, the controller 220 maycontrol the communication unit 210 to estimate and obtain new controlchannel information of the current TTI. The control channel informationof the current TTI that is newly estimated and obtained by thecommunication unit 210 may be stored in the storage 230, and thecontroller 220 may control the communication unit 210 to use the controlchannel information of the current TTI stored in the storage 230 and todecode the control channel of the current TTI.

For reference, the TTI immediately after the channel characteristicmaintenance time has ended may mean the n+1 TTI when the last TTI of thechannel characteristic maintenance time is the n TTI.

Otherwise, when it is determined in operation S110 that the current TTIis not the TTI immediately after the channel characteristic maintenancetime has ended, the type of the different control channel informationmay be determined based on whether to maintain the channelcharacteristic between the current TTI and the immediately previous TTIof the current TTI in operations S115 to S138.

For reference, the case where the current TTI is not the TTI immediatelyafter the channel characteristic maintenance time has ended may mean acase where the last TTI of the channel characteristic maintenance timeis the n TTI, and the current TTI is a TTI equal to or greater than ann+2 TTI. In addition, when the current TTI is the n+2 TTI, theimmediately previous TTI of the current TTI may mean the n+1 TTI. Inthis case, the n+1 TTI is the TTI immediately after the channelcharacteristic maintenance time has ended. As described above, thecontrol channel of the n+1 TTI may be decoded based on the controlchannel information of the n+1 TTI.

In addition, whether to maintain the channel characteristic between thecurrent TTI and the immediately previous TTI of the current TTI may bedetermined based on the correlation between a channel estimation valueof the immediately previous TTI and a channel estimation value of thecurrent TTI or the Doppler spread estimation value of the immediatelyprevious TTI.

For reference, how to determine whether to maintain the channelcharacteristic between the current TTI and the immediately previous TTImay be set in advance by a user or a manufacturer. Accordingly, when‘NO’ is determined in operation S110, a corresponding operation may beperformed according to the type of a method of determining whether tomaintain the preset channel characteristic. For example, when acorrelation calculation method is preset, operations S115, S120, andS135 may proceed, and when a method of calculating the Doppler spreadestimation value is preset, operations S125, S130, and S138 may proceed.That is, whether to maintain the channel characteristic may bedetermined based on any one of the correlation calculation method andthe Doppler spread estimation value calculation method.

Here, the correlation between the channel estimation value of theimmediately previous TTI and the channel estimation value of the currentTTI may be calculated by the following Equation 1.

$\begin{matrix}{{correlation} = {\frac{E\left\{ {{\overset{\sim}{H}}_{n}{\overset{\sim}{H}}_{({n - 1})}^{*}} \right\}}{E\left\{ {❘{\overset{\sim}{H}}_{n}❘}^{2} \right\}} < \gamma_{1}}} & \left( {{Equation}1} \right)\end{matrix}$

{tilde over (H)}_(n) and {tilde over (H)}_((n-1)) may denote a channelestimation value of the n TTI and a channel estimation value of the n−1TTI, respectively, and a first reference value γ1 may denote a referencevalue with respect to the correlation between channels of adjacent TTIs.In addition, E{ } may denote a probability mean, and * may denote acomplex conjugate. γ1 may be predefined, for example by a user ormanufacturer, as an arbitrary value between 0 and 1.

In addition, it may be determined whether the channel characteristic ismaintained between the current TTI and the immediately previous TTI ofthe current TTI through comparison between the correlation and the firstreference value γ1.

That is, when the correlation is less than the first reference value γ1,it may be determined that the channel characteristic between the currentTTI and the immediately previous TTI of the current TTI does not remainthe same. Otherwise, when the correlation is greater than or equal tothe first reference value γ1, it may be determined that the channelcharacteristic between the current TTI and the immediately previous TTIof the current TTI remains the same.

For reference, the closer the correlation is to 1, the greater thesimilarity of the channel characteristic between the current TTI and theimmediately previous TTI of the current TTI, and the closer thecorrelation is to 0, the smaller the similarity of the channelcharacteristic between the current TTI and the immediately previous TTIof the current TTI.

In addition, when it is determined whether the channel characteristic ismaintained based on the correlation between the channel estimationvalues, the controller 220 may read the control channel estimation valueof the immediately previous TTI stored in the storage 230 and controlthe communication unit 210 to obtain a new control channel estimationvalue of the current TTI. Here, the controller 220 may control thecommunication unit 210 to estimate and obtain new control channelinformation other than the control channel estimation value of thecurrent TTI.

In addition, the control channel information of the current TTI that isnewly estimated and obtained by the communication unit 210 may be storedin the storage 230, and the controller 220 may calculate a correlationbetween the channel estimation value of the immediately previous TTI andthe channel estimation value of the current TTI based on the controlchannel estimation value of the immediately previous TTI read from thestorage 230 and the control channel estimation value of the current TTIthat is newly obtained by the communication unit 210. Furthermore, thecontroller 220 may determine whether maintain the channel characteristicis maintained between the current TTI and the immediately previous TTIby comparing the correlation between the channel estimation values withthe first reference value γ1.

Based on the correlation between the channel estimation value of theimmediately previous TTI and the channel estimation value of the currentTTI calculated as described above, it may be determined whether thechannel characteristic is maintained between the current TTI and theimmediately previous TTI.

In embodiments, the other control channel information may be determinedas follows based on the method of determining whether to maintain thechannel characteristic described above.

Specifically, when it is determined in operation S115 that thecorrelation between the channel estimation value of the immediatelyprevious TTI and the channel estimation value of the current TTIindicates that the channel characteristic between the current TTI andthe immediately previous TTI is maintained, at operation S120 the othercontrol channel information may include the control channel informationnewly obtained in the current TTI, and the channel characteristicmaintenance time may restart with respect to an immediately followingTTI of the current TTI.

That is, when the correlation between the channel estimation valuesindicates that the channel characteristic between the current TTI andthe immediately previous TTI is maintained, for example when thecorrelation between the channel estimation values is greater than orequal to the first reference value γ1, the controller 220 may controlthe communication unit 210 to decode the control channel of the currentTTI by using the control channel information of the current TTI storedin the storage 230.

In addition, the controller 220 controls the communication unit 210 suchthat the channel characteristic maintenance time restarts with respectto the immediately following TTI (e.g., an n+3 TTI) of the current TTI(e.g., an n+2 TTI), and thus, control channels of all TTIs including theimmediately following TTI within the channel characteristic maintenancetime may be decoded based on the control channel information of thecurrent TTI.

Otherwise, when it is determined in operation S115 that the correlationbetween the channel estimation value of the immediately previous TTI andthe channel estimation value of the current TTI indicates that thechannel characteristic between the current TTI and the immediatelyprevious TTI is not maintained, at operation S135 the other controlchannel information may include the control channel information newlyobtained in the current TTI.

That is, when the correlation between the channel estimation valuesindicates that the channel characteristic between the current TTI andthe immediately previous TTI is not maintained, for example when thecorrelation between the channel estimation values is less than the firstreference value γ1, the controller 220 may control the communicationunit 210 to decode the control channel of the current TTI by using thecontrol channel information of the current TTI stored in the storage230.

For reference, when operation S100 is completed with operation S135,when the immediately following TTI (e.g., the n+3 TTI) of the currentTTI (e.g., the n+2 TTI) arrives, the controller 220 may repeat the sameoperation as operation S115 on the current TTI and the following TTI.

That is, the controller 220 may read the channel estimation value of thecurrent TTI (e.g., n+2 TTI) stored in the storage 230, and control thecommunication unit 210 to obtain a new control channel estimation valueof the immediately following TTI (e.g., the n+3 TTI) of the current TTI.Here, the controller 220 may control the communication unit 210 toestimate and obtain new control channel information other than thecontrol channel estimation value of the immediately following TTI.

The control channel information of the immediately following TTI that isnewly estimated and obtained by the communication unit 210 may be storedin the storage 230, and the controller 220 may calculate a correlationbetween the channel estimation value of the current TTI and the channelestimation value of the following TTI based on the control channelestimation value of the current TTI read from the storage 230 and thecontrol channel estimation value of the following TTI that is newlyobtained by the communication unit 210. Furthermore, the controller 220may determine whether maintain a channel characteristic is maintainedbetween the current TTI and the immediately following TTI by comparingthe correlation between the channel estimation values with the firstreference value γ1.

In embodiments, as described above, the other control channelinformation may be determined by using another method of determiningwhether the channel characteristic is maintained.

That is, whether maintain the channel characteristic is maintainedbetween the current TTI and the immediately previous TTI of the currentTTI may be determined based on the Doppler spread estimation value ofthe immediately previous TTI.

Here, the Doppler spread estimation value of the immediately previousTTI (e.g., the n−1 TTI when the current TTI is the n TTI) may becompared with a reference value as in the following Equation 2.

Doppler spread estimation value=D _((n-1))<γ₂  (Equation 2)

D_((n-1)) may denote the Doppler spread estimation value of the n−1 TTI,and a second reference value γ2 may denote a reference value withrespect to the Doppler spread. For reference, the Doppler spreadestimation value may increase as the relative speed between a terminaland a base station increases. γ2 may expressed in a unit of Hz, and maybe predefined, for example by a user or manufacturer, as an arbitraryvalue greater than 0.

In addition, it may be determined whether the channel characteristic ismaintained between the current TTI and the immediately previous TTIthrough comparison between the Doppler spread estimation value and thesecond reference value γ2.

That is, when the Doppler spread estimation value is less than thesecond reference value γ2, it may be determined that the channelcharacteristic between the current TTI and the immediately previous TTIof the current TTI remains the same. Otherwise, when the Doppler spreadestimation value is greater than or equal to the second reference valueγ2, it may be determined that the channel characteristic between thecurrent TTI and the immediately previous TTI of the current TTI does notremain the same.

For reference, the closer the Doppler spread estimation value is to 0,the greater the similarity of the channel characteristic between thecurrent TTI and the immediately previous TTI of the current TTI, and thegreater the Doppler spread estimation value (e.g., when the Dopplerspread estimation value exceeds 30 Hz), the smaller the similarity ofthe channel characteristic between the current TTI and the immediatelyprevious TTI of the current TTI.

In addition, when it is determined whether the channel characteristic ismaintained based on the Doppler spread estimation value, the controller220 may read the Doppler spread estimation value of the immediatelyprevious TTI stored in the storage 230.

In addition, the controller 220 may compare the Doppler spreadestimation value of the immediately previous TTI read from the storage230 with the second reference value γ2 to determine whether to maintainthe channel characteristic between the current TTI and the immediatelyprevious TTI.

Based on the Doppler spread estimation value of the immediately previousTTI calculated as described above, it may be determined whether thechannel characteristic is maintained between the current TTI and theimmediately previous TTI.

In embodiments, the other control channel information may be determinedas follows based on the method of determining whether the channelcharacteristic is maintained described above.

Specifically, when it is determined in operation S125 that the Dopplerspread estimation value of the immediately previous TTI indicates thatthe channel characteristic between the current TTI and the immediatelyprevious TTI is maintained, the other control channel information mayinclude the control channel information obtained in the immediatelyprevious TTI, and the channel characteristic maintenance time mayrestart with respect to the current TTI in operation S130.

That is, when the Doppler spread estimation value indicates that thechannel characteristic between the current TTI and the immediatelyprevious TTI is maintained, for example when the Doppler spreadestimation value is less than the second reference value γ2, thecontroller 220 may control the communication unit 210 to decode thecontrol channel of the current TTI by using the control channelinformation of the immediately previous TTI stored in the storage 230.

In addition, the controller 220 controls the communication unit 210 suchthat the channel characteristic maintenance time restarts with respectto the current TTI (e.g., the n TTI), and thus, control channels of allTTIs including the current TTI within the channel characteristicmaintenance time may be decoded based on the control channel informationof the immediately previous TTI.

Otherwise, when it is determined in operation S125 that the Dopplerspread estimation value of the immediately previous TTI indicates thatthe channel characteristic between the current TTI and the immediatelyprevious TTI is not maintained, the other control channel informationmay include the control channel information newly obtained in thecurrent TTI in operation S138.

That is, when the Doppler spread estimation value indicates that thechannel characteristic between the current TTI and the immediatelyprevious TTI is not maintained, for example when the Doppler spreadestimation value is greater than or equal to the second reference valueγ2, the controller 220 may control the communication unit 210 to obtainnew control channel information of the current TTI.

The control channel information of the current TTI that is newlyestimated and obtained by the communication unit 210 may be stored inthe storage 230, and the controller 220 may control the communicationunit 210 to decode the control channel of the current TTI by using thecontrol channel information of the current TTI stored in the storage230.

For reference, when operation S100 is completed with operation S138,when an immediately following TTI (e.g., the n+1 TTI) of the current TTI(e.g., the n TTI) arrives, the controller 220 may repeat operation S125on the current TTI and the immediately following TTI.

That is, the controller 220 may read the Doppler spread estimation valueof the current TTI stored in the storage 230. In addition, thecontroller 220 may compare the Doppler spread estimation value of thecurrent TTI read from the storage 230 with the second reference value γ2to determine whether the channel characteristic is maintained betweenthe current TTI and the immediately following TTI.

For reference, in addition to the above-described two methods ofdetermining whether maintain the channel characteristics are maintained,a method of determining whether maintain channel characteristic ismaintained using various channel information may be used, and thus, adetailed description thereof is omitted.

Referring back to FIG. 7 , the control channel of the current TTI isdecoded based on the determination result of operation S100 in operationS200.

Specifically, the controller 220 may control the communication unit 210to decode the control channel of the current TTI based on thedetermination result obtained through operation S100.

In particular, the controller 220 may control a decoder of thecommunication unit 210 based on the determination result obtainedthrough operation S100.

When the control channel of the current TTI is decoded in operationS200, it is determined whether there is a data channel in the currentTTI based on a decoding result in operation S300.

Specifically, the communication unit 210 may obtain a variety ofinformation, for example downlink data grant, downlink data format,uplink data grant, uplink data format, uplink power control, etc., bydecoding the control channel of the current TTI, and the obtainedinformation may be stored in the storage 230 by the controller 220.

When a decoding operation is completed, the controller 220 may determinewhether there is a data channel in the current TTI based on whether thedownlink data grant is included in the variety of information obtainedthrough the decoding operation.

When it is determined whether there is a data channel in the current TTIin operation S300, it is determined whether to turn off thecommunication unit 210 that processes the received signal based on thedetermination result in operation S400.

Here, referring to FIG. 9 , an example of operation S400 is shown indetail below, according to an embodiment.

Specifically, when it is determined that there is a data channel in thecurrent TTI based on the decoding result in operation S300, thenoperation S400 may include operation S410 of maintaining thecommunication unit 210 in an on state, operation S415 of determiningwhether to decode the data channel of the current TTI based on the datachannel information of the immediately previous TTI, and operation S480of decoding the data channel of the current TTI based on thedetermination result.

That is, when there is a data channel in the current TTI, thecommunication unit 210 may be used to decode the data channel of thecurrent TTI, and thus, the controller 220 may maintain the communicationunit 210 in the on state.

In addition, the controller 220 may determine whether to decode the datachannel of the current TTI based on the data channel information of theimmediately previous TTI. Here, the data channel information of theimmediately previous TTI may be stored in the storage 230, and thecontroller 220 may retrieve and use the data channel information of theimmediately previous TTI stored in the storage 230 through a readoperation as necessary.

In embodiments, as shown for example in FIG. 10 , operation S415 mayinclude operation S420 of checking whether the channel characteristicmaintenance time has ended and operations S422 to S453 of determiningwhether to reuse the data channel information of the immediatelyprevious TTI based on a check result.

That is, when it is determined that there is a data channel in thecurrent TTI, the controller 220 may check whether the channelcharacteristic maintenance time has ended, and determine whether toreuse the data channel information of the immediately previous TTI inthe current TTI based on the check result.

Here, referring to FIG. 10 , an example of operation S415 is shown indetail below, according to an embodiment.

Operation S415 of determining whether to decode the data channel of thecurrent TTI based on the data channel information of the immediatelyprevious TTI may start with operation S420 of determining whether thechannel characteristic maintenance time has ended.

Specifically, when it is determined that the channel characteristicmaintenance time has not ended in operation S420, the data channelinformation of the immediately previous TTI may be reused for the datachannel decoding of the current TTI in operation S422.

That is, when the channel characteristic maintenance time has not ended,the controller 220 may control the communication unit 210 to reuse thedata channel information of the immediately previous TTI stored in thestorage 230 and to decode the data channel of the current TTI.

In embodiments, when it is determined that the channel characteristicmaintenance time has ended in operation S420, the data channelinformation of the immediately previous TTI is not reused for the datachannel decoding of the current TTI, and data channel informationdifferent from the data channel information of the immediately previousTTI may be used for the data channel decoding of the current TTI.

Specifically, when the current TTI is a TTI immediately after thechannel characteristic maintenance time has ended at operation S425, thedifferent data channel information may include data channel informationnewly obtained from the current TTI. In this case, the data channelinformation newly obtained from the current TTI, for example datachannel information of the current TTI, may be used for data channeldecoding of the current TTI at operation S427.

That is, when the current TTI is the TTI immediately after the channelcharacteristic maintenance time has ended, the controller 220 maycontrol the communication unit 210 to estimate and obtain new datachannel information of the current TTI. The data channel information ofthe current TTI that is newly estimated and obtained by thecommunication unit 210 may be stored in the storage 230, and thecontroller 220 may control the communication unit 210 to use the datachannel information of the current TTI stored in the storage 230 and todecode the data channel of the current TTI.

For reference, the TTI immediately after the channel characteristicmaintenance time has ended may mean the n+1 TTI when the last TTI of thechannel characteristic maintenance time is the n TTI.

In embodiments, when it is determined in operation S425 that the currentTTI is not the TTI immediately after the channel characteristicmaintenance time has ended, the type of the different control channelinformation may be determined based on whether to maintain the channelcharacteristic between the current TTI and the immediately previous TTIof the current TTI in operations S430 to S453.

For reference, the case where the current TTI is not the TTI immediatelyafter the channel characteristic maintenance time has ended may mean acase where the last TTI of the channel characteristic maintenance timeis the n TTI, and the current TTI is a TTI equal to or greater than ann+2 TTI. In addition, when the current TTI is the n+2 TTI, theimmediately previous TTI of the current TTI may mean the n+1 TTI. Inthis case, the n+1 TTI is the TTI immediately after the channelcharacteristic maintenance time has ended. As described above, the datachannel of the n+1 TTI may be decoded based on the data channelinformation of the n+1 TTI.

In addition, whether the channel characteristic is maintained betweenthe current TTI and the immediately previous TTI of the current TTI maybe determined based on the correlation between a channel estimationvalue of the immediately previous TTI and a channel estimation value ofthe current TTI or the Doppler spread estimation value of theimmediately previous TTI.

For reference, method used to determine whether the channelcharacteristic is maintained between the current TTI and the immediatelyprevious TTI may be set in advance, for example by a user or amanufacturer. Accordingly, when ‘NO’ is determined in S425, acorresponding operation may be performed according to the type of amethod of determining whether the preset channel characteristic ismaintained. For example, when a correlation calculation method ispreset, operations S430, S435, and S450 may proceed, and when a methodof calculating the Doppler spread estimation value is preset, operationsS440, S445, and S453 may proceed.

Here, the correlation between the channel estimation value of theimmediately previous TTI and the channel estimation value of the currentTTI may be calculated by the following Equation 3.

$\begin{matrix}{{correlation} = {\frac{E\left\{ {{\overset{\sim}{H}}_{n}{\overset{\sim}{H}}_{({n - 1})}^{*}} \right\}}{E\left\{ {❘{\overset{\sim}{H}}_{n}❘}^{2} \right\}} < \gamma_{1}}} & \left( {{Equation}3} \right)\end{matrix}$

{tilde over (H)}_(n) and {tilde over (H)}_((n-1)) may denote a channelestimation value of the n TTI and a channel estimation value of the n−1TTI, respectively, and a first reference value γ1 may denote a referencevalue with respect to the correlation between channels of adjacent TTIs.In addition, E{ } may denote a probability mean, and * may denote acomplex conjugate. γ1 may be predefined, for example by a user ormanufacturer, as an arbitrary value between 0 and 1.

In addition, it may be determined whether the channel characteristic ismaintained between the current TTI and the immediately previous TTI ofthe current TTI through comparison between the correlation and the firstreference value γ1.

That is, when the correlation is less than the first reference value γ1,it may be determined that the channel characteristic between the currentTTI and the immediately previous TTI of the current TTI does not remainthe same. In embodiments, when the correlation is greater than or equalto the first reference value γ1, it may be determined that the channelcharacteristic between the current TTI and the immediately previous TTIof the current TTI remains the same.

For reference, the closer the correlation is to 1, the greater thesimilarity of the channel characteristic between the current TTI and theimmediately previous TTI of the current TTI, and the closer thecorrelation is to 0, the smaller the similarity of the channelcharacteristic between the current TTI and the immediately previous TTIof the current TTI.

In addition, when it is determined whether the channel characteristic ismaintained based on the correlation between the channel estimationvalues, the controller 220 may read the data channel estimation value ofthe immediately previous TTI stored in the storage 230 and control thecommunication unit 210 to obtain a new data channel estimation value ofthe current TTI. Here, the controller 220 may control the communicationunit 210 to estimate and obtain new data channel information other thanthe data channel estimation value of the current TTI.

In addition, the data channel information of the current TTI that isnewly estimated and obtained by the communication unit 210 may be storedin the storage 230, and the controller 220 may calculate a correlationbetween the channel estimation value of the immediately previous TTI andthe channel estimation value of the current TTI based on the datachannel estimation value of the immediately previous TTI read from thestorage 230 and the data channel estimation value of the current TTIthat is newly obtained by the communication unit 210. Furthermore, thecontroller 220 may determine whether to maintain the channelcharacteristic between the current TTI and the immediately previous TTIby comparing the correlation between the channel estimation values withthe first reference value γ1.

Based on the correlation between the channel estimation value of theimmediately previous TTI and the channel estimation value of the currentTTI calculated as described above, it may be determined whether thechannel characteristic is maintained between the current TTI and theimmediately previous TTI.

In embodiments, the other data channel information may be determined asfollows based on the method of determining whether the channelcharacteristic is maintained described above.

Specifically, when it is determined in operation S430 that thecorrelation between the channel estimation value of the immediatelyprevious TTI and the channel estimation value of the current TTIindicates that the channel characteristic between the current TTI andthe immediately previous TTI is maintained, the other data channelinformation may include the data channel information newly obtained inthe current TTI, and the channel characteristic maintenance time mayrestart with respect to an immediately following TTI of the current TTIin operation S435.

That is, when the correlation between the channel estimation valuesindicates that the channel characteristic between the current TTI andthe immediately previous TTI is maintained, for example when thecorrelation between the channel estimation values is greater than orequal to the first reference value γ1, the controller 220 may controlthe communication unit 210 to decode the data channel of the current TTIby using the data channel information of the current TTI stored in thestorage 230.

In addition, the controller 220 controls the communication unit 210 suchthat the channel characteristic maintenance time restarts with respectto the immediately following TTI (e.g., the n+3 TTI) of the current TTI(e.g., the n+2 TTI), and thus data channels of all TTIs including thefollowing TTI within the channel characteristic maintenance time may bedecoded based on the data channel information of the current TTI.

In embodiments, when it is determined in operation S430 that thecorrelation between the channel estimation value of the immediatelyprevious TTI and the channel estimation value of the current TTIindicates that the channel characteristic between the current TTI andthe immediately previous TTI is not maintained, the other controlchannel information may include the data channel information newlyobtained in the current TTI in operation S450.

That is, when the correlation between the channel estimation valuesindicates that the channel characteristic between the current TTI andthe immediately previous TTI is not maintained, for example when thecorrelation between the channel estimation values is less than the firstreference value γ1, the controller 220 may control the communicationunit 210 to decode the data channel of the current TTI by using the datachannel information of the current TTI stored in the storage 230.

For reference, when operation S415 is completed with operation S450,when the immediately following TTI (e.g., the n+3 TTI) of the currentTTI (e.g., the n+2 TTI) arrives, the controller 220 may repeat the sameoperation as operation S430 on the current TTI and the following TTI.

That is, the controller 220 may read the channel estimation value of thecurrent TTI (e.g., the n+2 TTI) stored in the storage 230, and controlthe communication unit 210 to obtain a new data channel estimation valueof the immediately following TTI (e.g., the n+3 TTI) of the current TTI.Here, the controller 220 may control the communication unit 210 toestimate and obtain new data channel information other than the datachannel estimation value of the immediately following TTI.

The data channel information of the immediately following TTI that isnewly estimated and obtained by the communication unit 210 may be storedin the storage 230, and the controller 220 may calculate a correlationbetween the channel estimation value of the current TTI and the channelestimation value of the following TTI based on the data channelestimation value of the current TTI read from the storage 230 and thedata channel estimation value of the following TTI that is newlyobtained by the communication unit 210. Furthermore, the controller 220may determine whether to maintain a channel characteristic between thecurrent TTI and the immediately following TTI by comparing thecorrelation between the channel estimation values with the firstreference value γ1.

In embodiments, as described above, the other data channel informationmay be determined by using another method of determining whether thechannel characteristic is maintained.

That is, whether the channel characteristic is maintained between thecurrent TTI and the immediately previous TTI of the current TTI may bedetermined based on the Doppler spread estimation value of theimmediately previous TTI.

Here, the Doppler spread estimation value of the immediately previousTTI (e.g., the n−1 TTI; the current TTI is the n TTI) may be comparedwith a reference value as in the following Equation 4.

Doppler spread estimation value=D _((n-1))<γ₂  (Equation 4)

D_((n-1)) may denote the Doppler spread estimation value of the n−1 TTI,and a second reference value γ2 may denote a reference value withrespect to the Doppler spread. For reference, the Doppler spreadestimation value may increase as the relative speed between a terminaland a base station increases. γ2 may be expressed in a unit of Hz, andmay be predefined, for example by a user or manufacturer, as anarbitrary value greater than 0.

In addition, it may be determined whether the channel characteristic ismaintained between the current TTI and the immediately previous TTIthrough comparison between the Doppler spread estimation value and thesecond reference value γ2.

That is, when the Doppler spread estimation value is less than thesecond reference value γ2, it may be determined that the channelcharacteristic between the current TTI and the immediately previous TTIof the current TTI remains the same. In embodiments, when the Dopplerspread estimation value is greater than or equal to the second referencevalue γ2, it may be determined that the channel characteristic betweenthe current TTI and the immediately previous TTI of the current TTI doesnot remain the same.

For reference, the closer the Doppler spread estimation value is to 0,the greater the similarity of the channel characteristic between thecurrent TTI and the immediately previous TTI of the current TTI, and thegreater the Doppler spread estimation value (e.g., when the Dopplerspread estimation value exceeds 30 Hz), the smaller the similarity ofthe channel characteristic between the current TTI and the immediatelyprevious TTI of the current TTI.

In addition, when it is determined whether the channel characteristic ismaintained based on the Doppler spread estimation value, the controller220 may read the Doppler spread estimation value of the immediatelyprevious TTI stored in the storage 230.

In addition, the controller 220 may compare the Doppler spreadestimation value of the immediately previous TTI read from the storage230 with the second reference value γ2 to determine whether the channelcharacteristic is maintained between the current TTI and the immediatelyprevious TTI.

Based on the Doppler spread estimation value of the immediately previousTTI calculated as described above, it may be determined whether thechannel characteristic is maintained between the current TTI and theimmediately previous TTI.

In embodiments, the other data channel information may be determined asfollows based on the method of determining whether to maintain thechannel characteristic described above.

Specifically, when it is determined in operation S440 that the Dopplerspread estimation value of the immediately previous TTI indicates thatthe channel characteristic between the current TTI and the immediatelyprevious TTI is maintained, the other data channel information mayinclude the data channel information obtained in the immediatelyprevious TTI, and the channel characteristic maintenance time mayrestart with respect to the current TTI in operation S445.

That is, when the Doppler spread estimation value indicates that thechannel characteristic between the current TTI and the immediatelyprevious TTI is maintained, for example when the Doppler spreadestimation value is smaller than the second reference value γ2, thecontroller 220 may control the communication unit 210 to decode the datachannel of the current TTI by using the data channel information of theimmediately previous TTI stored in the storage 230.

In addition, the controller 220 controls the communication unit 210 suchthat the channel characteristic maintenance time restarts with respectto the current TTI (e.g., the n TTI), and thus data channels of all TTIsincluding the current TTI within the channel characteristic maintenancetime may be decoded based on the data channel information of theimmediately previous TTI.

In embodiments, when it is determined in operation S440 that the Dopplerspread estimation value of the immediately previous TTI indicates thatthe channel characteristic between the current TTI and the immediatelyprevious TTI is not maintained, the other data channel information mayinclude the data channel information newly obtained in the current TTIin operation S453.

That is, when the Doppler spread estimation value indicates that thechannel characteristic between the current TTI and the immediatelyprevious TTI is not maintained, for example when the Doppler spreadestimation value is greater than or equal to the second reference valueγ2, the controller 220 may control the communication unit 210 to obtainnew data channel information of the current TTI.

The data channel information of the current TTI that is newly estimatedand obtained by the communication unit 210 may be stored in the storage230, and the controller 220 may control the communication unit 210 todecode the data channel of the current TTI by using the data channelinformation of the current TTI stored in the storage 230.

For reference, when an immediately following TTI (e.g., the n+1 TTI) ofthe current TTI (e.g., the n TTI) arrives after operation S415 iscompleted with operation S453, the controller 220 may repeat operationS440 on the current TTI and the following TTI.

That is, the controller 220 may read the Doppler spread estimation valueof the current TTI stored in storage 230. In addition, the controller220 may compare the Doppler spread estimation value of the current TTIread from the storage 230 with the second reference value γ2 todetermine whether to maintain the channel characteristic between thecurrent TTI and the immediately following TTI.

For reference, in addition to the above-described two methods ofdetermining whether the channel characteristics are maintained, a methodof determining whether the channel characteristic is maintained usingvarious channel information may be used, and thus, a detaileddescription thereof is omitted.

Referring back to FIG. 9 , the data channel of the current TTI may bedecoded based on the determination result of operation S415 in operationS480.

Specifically, the controller 220 may control the communication unit 210to decode the data channel of the current TTI based on the determinationresult obtained through operation S415.

In particular, the controller 220 may control a decoder of thecommunication unit 210 based on the determination result obtainedthrough operation S415.

In embodiments, when it is determined that there is not a data channelin the current TTI based on the decoding result in operation S300 o,operation S400 may include operation S412 of turning off some componentsof the communication unit 210.

That is, when there is not a data channel in the current TTI, for savingpower, the communication unit 210 may turn off some components of thecommunication unit 210.

Specifically, the controller 220 may turn off some components of thecommunication unit 210, switch some other components of thecommunication unit 210 to a standby state or a sleep state, and maintainthe remaining components of the communication unit 210 in an always onstate in operation S412.

That is, based on the method described above in FIG. 4 , the controller220 may selectively turn off each component in the communication unit210.

As described above, the receiver 120 of FIG. 1 may be driven by usingthe above-described wireless communication method to reduce powerconsumed when receiving data. Hereinafter, other examples of thewireless communication method of the receiver of FIG. 1 will bedescribed with reference to FIGS. 11 and 12 .

For reference, the wireless communication methods shown in FIGS. 11 and12 may correspond to the wireless communication method of FIG. 7 exceptfor some operations, and thus differences will be mainly described.

Referring to FIG. 11 , unlike the wireless communication method of FIG.7 , first, information about whether beamforming characteristic is thesame is received in operation S90.

Specifically, the communication unit 210 may receive information aboutwhether the beamforming characteristic applied to a immediately previousTTI and a current TTI are the same from the transmitter 110, for examplea base station.

Here, the information about whether the beamforming characteristic isthe same may be provided to the receiver 120, for example a terminal,through Radio Resource Control (RRC) Signaling or Downlink ControlInformation (DCI) transmission from the transmitter 110

When the information about whether the beamforming characteristic is thesame is received in operation S90, it is determined whether to decode acontrol channel of the current TTI based on control channel informationof the immediately previous TTI in operation S100.

Specifically, operation S100 of determining whether to decode thecontrol channel of the current TTI based on the control channelinformation of the immediately previous TTI may include operation S101of checking whether the beamforming characteristic applied to theimmediately previous TTI and the current TTI are the same based on theinformation about whether the received beamforming characteristic is thesame and operations (e.g. operations S105 to S138 in FIG. 8 ) ofdetermining whether to reuse the control channel information of theimmediately previous TTI based on a check result.

That is, the communication unit 210 may receive information related tothe beamforming characteristic through RRC signaling or DCI transmissionfrom the transmitter 110 and provide the received information related tothe beamforming characteristic to the controller 220. In addition, thecontroller 220 may check whether the beamforming characteristic appliedto the immediately previous TTI and the current TTI are the same basedon the information related to the beamforming characteristic providedfrom the communication unit 210. Furthermore, the controller 220 maydetermine whether to reuse the control channel information of theimmediately previous TTI based on the check result.

Accordingly as compared to FIG. 7 , FIG. 11 shows an embodiment furtherincluding operations S90 and S101.

For reference, in order to increase the quality of a transmissionsignal, for example the signal that the transmitter 110 transmits to thereceiver 120, beamforming may be applied to the transmission signal.Here, the meaning that beamforming is applied to the transmission signalmay mean that the transmission signal is precoded.

However, when different beamforming is applied to each TTI, a wirelesschannel characteristic of the signal transmitted in each TTI to thereceiver 120 may vary.

As described above, when the wireless channel characteristics change bybeamforming, in the embodiment, the transmitter 110 provides beamformingrelated information to the receiver 120 through signaling, which may behelpful in improving power saving of the receiver 120.

Specifically, for example, when the receiver 120 obtains beamformingcharacteristic maintenance information (that is, information that thebeamforming characteristic remains the same during two consecutive TTIs)through signaling from the transmitter 110, power saving mechanismaccording to a channel adaptive power control mode as shown in FIG. 4may be performed in the receiver 120. When the beamformingcharacteristic applied during two consecutive TTIs are different, thereceiver 120 does not use the channel information of the immediatelyprevious TTI for a channel decoding operation of the current TTI.

Based on this principle, FIG. 11 will be described in more detail asfollows.

Specifically, when it is determined that the beamforming characteristicis the same in operation S101 of checking whether the beamformingcharacteristic applied to the immediately previous TTI and the currentTTI are the same, it may be determined whether to reuse the controlchannel information of the immediately previous TTI based on whether thechannel characteristic maintenance time has ended in operation S105.

That is, when it is determined in operation S101 that the beamformingcharacteristic is the same in the two TTIs, operation S105 describedabove in FIG. 8 may proceed. A more detailed description of an exampleof operation S105 is as follows.

When it is determined in operation S105 that the channel characteristicmaintenance time has not ended, the control channel information of theimmediately previous TTI may be reused for control channel decoding ofthe current TTI in operation S107.

Specifically, when the channel characteristic maintenance time has notended, the controller 220 may control the communication unit 210 toreuse the control channel information of the immediately previous TTIstored in the storage 230 and to decode the control channel of thecurrent TTI.

That is, when it is determined in operation S105 that the channelcharacteristic maintenance time has not ended, operation S107 describedabove in FIG. 8 may proceed.

In embodiments, when it is determined that the channel characteristicmaintenance time has ended at operation S105, the control channelinformation of the immediately previous TTI is not reused for thecontrol channel decoding of the current TTI, and control channelinformation different from the control channel information of theimmediately previous TTI may be used for the control channel decoding ofthe current TTI in operations S110 to S138.

Specifically, when the channel characteristic maintenance time hasended, the controller 220 may control the communication unit 210 to usecontrol channel information different from the control channelinformation of the immediately previous TTI and to decode the controlchannel of the current TTI.

That is, when it is determined that the channel characteristicmaintenance time has ended in operation S105, operation S110 describedabove in FIG. 8 may proceed.

In embodiments, when it is determined that the beamformingcharacteristics are not the same in operation S101, the control channelinformation of the immediately previous TTI is not reused for thecontrol channel decoding of the current TTI, and control channelinformation newly obtained in the current TTI may be used for thecontrol channel decoding of the current TTI.

Specifically, when the beamforming characteristic between theimmediately previous TTI and the current TTI does not remain the same,the controller 220 may control the communication unit 210 to obtain newcontrol channel information of the current TTI. In addition, the controlchannel information of the current TTI that is newly estimated andobtained by the communication unit 210 may be stored in the storage 230,and the controller 220 may control the communication unit 210 to decodethe control channel of the current TTI by using the control channelinformation of the current TTI stored in the storage 230.

That is, when it is determined in operation S101 that the beamformingcharacteristic does not remain the same in the two TTIs, operation S112described above in FIG. 8 may proceed.

For reference, for convenience of explanation, operations afteroperations S105 and S112 are not specifically shown in operation S100 ofFIG. 11 , but as described above, operations after operations S105 andS112 may proceed as detailed operation S100 of FIG. 8 . In addition,when operation S100 of FIG. 11 is completed, operations S200 to S400 maybe sequentially performed as shown in FIG. 7 .

The embodiment of FIG. 11 includes operation S90 of receiving theinformation about whether the beamforming characteristic is the same andoperation S101 of checking whether the beamforming characteristicapplied to the immediately previous TTI and the current TTI are thesame, and thus, the power saving mechanism of the receiver 120 may beimproved.

Subsequently, referring to FIG. 12 , unlike the wireless communicationmethod of FIG. 11 , operation S95 of requesting the transmitter 110, forexample the base station, to transmit a control channel DemodulationReference Signal (DMRS) mapped to resources throughout the entire bandmay be additionally performed before operation S100.

Here, when the receiver 120, for example the terminal, requests thetransmitter 110 to transmit the control channel DMRS, the controlchannel DMRS transmitted from the transmitter 110 to the receiver 120may be mapped to resources throughout the entire band.

For reference, in the embodiment of FIG. 12 , it is shown that operationS95 proceeds after operation S90, for example an operation of receivingthe information about whether the beamforming characteristic is thesame, but is not limited thereto. That is, operation S90 and operationS95 may proceed simultaneously, or operation S95 may proceed beforeoperation S90. However, for convenience of explanation, it will bedescribed that operation S95 proceeds between operation S90 andoperation S100.

In embodiments, operation S100 of determining whether to decode thecontrol channel of the current TTI based on the control channelinformation of the immediately previous TTI may include operation S103of checking whether the beamforming characteristic applied to theimmediately previous TTI and the current TTI are the same based on theinformation about whether the received beamforming characteristic is thesame and checking whether resource mapping of the control channel DMRSof the immediately previous TTI and resource mapping of the controlchannel DMRS of the current TTI are the same and operations S105 to S138of FIG. 8 of determining whether to reuse the control channelinformation of the immediately previous TTI based on a check result.

For reference, in operation S103, the information about whether thebeamforming characteristic is the same may be provided to the receiver120 from the transmitter 110 through RRC signaling or DCI transmission.In addition, whether resource mapping of the control channel DMRS arethe same may be determined based on whether the control channel DMRS ofthe immediately previous TTI and the control channel DMRS of the currentTTI are mapped throughout the entire band.

Accordingly, the communication unit 210 may receive information relatedto the beamforming characteristic through RRC signaling or DCItransmission from the transmitter 110 and provide the receivedinformation related to the beamforming characteristic to the controller220. In addition, the controller 220 may check whether the beamformingcharacteristic applied to the immediately previous TTI and the currentTTI are the same based on the information related to the beamformingcharacteristic provided from the communication unit 210.

In addition, the controller 220 may request the transmitter 110 throughthe communication unit 210 to transmit the control channel DMRS mappedto resources throughout the entire band. In addition, the controller 220may check whether the control channel DMRS of the immediately previousTTI and the control channel DMRS of the current TTI received from thecommunication unit 210 are mapped to resources throughout the entireband and check whether resource mapping of the control channel DMRS ofthe immediately previous TTI and the current TTI are the same.

Further, the controller 220 may determine whether to reuse the controlchannel information of the immediately previous TTI based on the abovecheck results.

Accordingly as compared to FIG. 7 , FIG. 12 shows am embodiment furtherincluding operations S90, S95 and S103.

For reference, even when the beamforming characteristic of the signaltransmitted from the transmitter 110 to the receiver 120 remains thesame in two consecutive TTIs, if signals transmitted in the twoconsecutive TTIs are allocated to different frequency ranges, thewireless channel environment of the signals transmitted in the two TTIsmay be different.

In particular, in the case of a frequency-selective radio channel undera fading environment, characteristics of the radio channel may varygreatly depending on a frequency range in which a signal is transmitted.In this case, a channel estimation value obtained in the immediatelyprevious TTI may not be used to decode the signal received in thecurrent TTI.

In addition, the receiver 120 performs a channel estimation operation onthe control channel by using the control channel DMRS.

Accordingly, in the embodiment, when power saving of the receiver 120 isrequired, the receiver 120 may request the transmitter 110 to transmitthe control channel DMRS throughout the entire band (e.g., wideband) inorder to accurately determine whether to maintain the channelcharacteristic.

In this case, even when the actual control channel is allocated to somefrequency bands and transmitted, if the channel estimation operationDMRS with respect to the corresponding control channel is transmitted tothe entire band, the receiver 120 may obtain control channel estimationvalues with respect to all frequency ranges, for example the entireband. Accordingly, the receiver 120 may accurately determine whether tomaintain the channel characteristic, and as a result, the power savingmechanism according to the channel adaptive power control mode as shownin FIG. 4 may be performed in the receiver 120.

For reference, the receiver 120 uses the data channel DMRS whenperforming channel estimation on the data channel. Accordingly, duringthe data channel estimation operation, the receiver 120 may request thetransmitter 110 to transmit the data channel DMRS throughout the entireband (e.g., wideband).

Based on this principle, FIG. 12 will be described in more detail asfollows.

For reference, in the embodiment of FIG. 12 , it may be assumed that thereceiver 120 has received information that the beamformingcharacteristic remains the same in the immediately previous TTI and thecurrent TTI through signaling from the transmitter 110. That is, in theembodiment of FIG. 12 , it may be assumed that the beamformingcharacteristic remains the same in the immediately previous TTI and thecurrent TTI, and when the beamforming characteristic does not remain thesame, operation S112 of FIG. 11 may proceed.

Specifically, in operation S103 of checking whether the beamformingcharacteristic applied to the immediately previous TTI and the currentTTI are the same based on the information about whether the receivedbeamforming characteristic is the same and checking whether resourcemapping of the control channel DMRS of the immediately previous TTI andresource mapping of the control channel DMRS of the current TTI are thesame, when it is determined that both the beamforming characteristic andresource mapping of the control channel DMRS are the same, it may bedetermined whether to reuse the control channel information of theimmediately previous TTI based on whether the channel characteristicmaintenance time has ended in operation S105.

That is, when it is determined in operation S103 that both thebeamforming characteristic and the resource mapping remain the same inthe two TTIs, operation S105 described above in FIG. 8 may proceed. Amore detailed description of an example of operation S105 is as follows.

When it is determined in operation S105 that the channel characteristicmaintenance time has not ended, the control channel information of theimmediately previous TTI may be reused for control channel decoding ofthe current TTI in operation S107.

Specifically, when the channel characteristic maintenance time has notended, the controller 220 may control the communication unit 210 toreuse the control channel information of the immediately previous TTIstored in the storage 230 and to decode the control channel of thecurrent TTI.

That is, when it is determined in operation S105 that the channelcharacteristic maintenance time has not ended, operation S107 describedabove in FIG. 8 may proceed.

In embodiments, when it is determined in operation S105 that the channelcharacteristic maintenance time has ended, the control channelinformation of the immediately previous TTI is not reused for thecontrol channel decoding of the current TTI, and control channelinformation different from the control channel information of theimmediately previous TTI may be used for the control channel decoding ofthe current TTI in operations S110 to S138.

Specifically, when the channel characteristic maintenance time hasended, the controller 220 may control the communication unit 210 to usecontrol channel information different from the control channelinformation of the immediately previous TTI and to decode the controlchannel of the current TTI.

That is, when it is determined in operation S105 that the channelcharacteristic maintenance time has ended, operation S110 describedabove in FIG. 8 may proceed.

In embodiments, in operation S103 of checking whether the beamformingcharacteristic applied to the immediately previous TTI and the currentTTI is the same based on the information about whether the receivedbeamforming characteristic is the same and checking whether resourcemapping of the control channel DMRS of the immediately previous TTI andresource mapping of the control channel DMRS of the current TTI are thesame, when at least one of the beamforming characteristic and theresource mapping of the control channel DMRS is not the same, thecontrol channel information of the immediately previous TTI is notreused for the control channel decoding of the current TTI, and controlchannel information newly obtained in the current TTI may be used forthe control channel decoding of the current TTI in operation S112.

For reference, the above case may include at least one of, for example,a case where the beamforming characteristic is the same and the resourcemapping is different, a case where the beamforming characteristic isdifferent and the resource mapping is the same, and a case where boththe beamforming characteristic and the resource mapping are different.

Accordingly, when the beamforming characteristic or resource mapping inthe immediately previous TTI and the current TTI does not remain thesame, the controller 220 may control the communication unit 210 toobtain new control channel information of the current TTI. In addition,the control channel information of the current TTI that is newlyestimated and obtained by the communication unit 210 may be stored inthe storage 230, and the controller 220 may control the communicationunit 210 to decode the control channel of the current TTI by using thecontrol channel information of the current TTI stored in the storage230.

That is, when it is determined in operation S103 that the beamformingcharacteristic or resource mapping does not remain the same in the twoTTIs, operation S112 described above in FIG. 8 may proceed.

For reference, for convenience of explanation, in operation S100 of FIG.12 , operations after operations S105 and S112 are not specificallyshown, but as described above, operations after operations S105 and S112may proceed as in the detailed operation S100 of FIG. 8 . In addition,when operation S100 of FIG. 12 is completed, operations S200 to S400 maybe sequentially performed as shown in FIG. 7 .

The embodiment of FIG. 12 includes operation S90 of receiving theinformation about whether the beamforming characteristics are the same,operation S95 of requesting the transmitter 110 to transmit the controlchannel DMRS mapped to resources throughout the entire band, andoperation S103 of checking whether the beamforming characteristicsapplied to the immediately previous TTI and the current TTI are the sameand checking whether resource mapping of the control channel DMRS of theimmediately previous TTI and resource mapping of the control channelDMRS of the current TTI are the same, and thus, the power savingmechanism of the receiver 120 may be improved.

For reference, only descriptions related to the control channel areprovided in FIGS. 11 and 12 , but the embodiments of FIGS. 11 and 12 maybe applied to the data channel in the same manner. However, detailedinformation is omitted in this regard.

As described above, according to the exemplary embodiment, powerefficiency of the receiver may be improved by improving the power savingmechanism that reduces power consumed when the receiver receives data.

While embodiments have been particularly shown and described, it will beunderstood that various changes in form and details may be made thereinwithout departing from the spirit and scope of the following claims.

What is claimed is:
 1. A wireless communication method of a receiver,the wireless communication method comprising: performing a firstdetermination of whether to decode a control channel of a currenttransmission time interval (TTI) based on control channel information ofa previous TTI; decoding the control channel of the current TTI based ona result of the first determination; performing a second determinationof whether a data channel is included in the current TTI based on aresult of the decoding; and performing a third determination of whetherto deactivate a communication interface configured to process a receivedsignal based on a result of the second determination, wherein the firstdetermination comprises: checking whether a channel characteristicmaintenance time has ended; and determining whether to reuse the controlchannel information of the previous TTI based on a result of thechecking, wherein, based on the result of the checking indicating thatthe channel characteristic maintenance time has ended, different controlchannel information which is different from the control channelinformation of the previous TTI is used to decode the control channel ofthe current TTI without reusing the control channel information of theprevious TTI, and wherein, based on the current TTI not being a TTIimmediately following an end of the channel characteristic maintenancetime, a type of the different control channel information is determinedbased on whether a channel characteristic is maintained between thecurrent TTI and an immediately previous TTI of the current TTI.
 2. Thewireless communication method of claim 1, wherein whether the channelcharacteristic is maintained between the current TTI and the immediatelyprevious TTI is determined based on a correlation between a channelestimation value of the immediately previous TTI and a channelestimation value of the current TTI or a Doppler spread estimation valueof the immediately previous TTI.
 3. The wireless communication method ofclaim 2, wherein based on the correlation between the channel estimationvalue of the immediately previous TTI and the channel estimation valueof the current TTI indicating that the channel characteristic ismaintained between the current TTI and the immediately previous TTI: thedifferent control channel information comprises newly obtained controlchannel information of the current TTI, the channel characteristicmaintenance time is restarted with respect to an immediately followingTTI of the current TTI, and control channels of a plurality of TTIsincluding the immediately following TTI within the channelcharacteristic maintenance time are decoded based on the newly obtainedcontrol channel information of the current TTI.
 4. The wirelesscommunication method of claim 2, wherein, based on the correlationbetween the channel estimation value of the immediately previous TTI andthe channel estimation value of the current TTI indicating that thechannel characteristic is not maintained, the different control channelinformation comprises newly obtained control channel information of thecurrent TTI, and wherein the wireless communication method furthercomprises determining whether the channel characteristic is maintainedbetween the current TTI and an immediately following TTI of the currentTTI based on a correlation between the channel estimation value of thecurrent TTI and a channel estimation value of the immediately followingTTI.
 5. The wireless communication method of claim 2, wherein based onthe Doppler spread estimation value of the immediately previous TTIindicating that the channel characteristic is maintained between thecurrent TTI and the immediately previous TTI: the different controlchannel information comprises control channel information obtained fromthe immediately previous TTI, the channel characteristic maintenancetime is restarted with respect to the current TTI, and control channelsof a plurality of TTIs including the current TTI within the channelcharacteristic maintenance time are decoded based on the control channelinformation obtained from the immediately previous TTI.
 6. The wirelesscommunication method of claim 2, wherein, based on the Doppler spreadestimation value of the immediately previous TTI indicating that thechannel characteristic is not maintained between the current TTI and theimmediately previous TTI, the different control channel informationcomprises newly obtained control channel information of the current TTI,and wherein the wireless communication method further comprisesdetermining whether the channel characteristic is maintained between thecurrent TTI and an immediately following TTI of the current TTI based ona Doppler spread estimation value of the current TTI.
 7. A wirelesscommunication method of a receiver, the wireless communication methodcomprising: performing a first determination of whether to decode acontrol channel of a current transmission time interval (TTI) based oncontrol channel information of a previous TTI; decoding the controlchannel of the current TTI based on a result of the first determination;performing a second determination of whether a data channel is includedin the current TTI based on a result of the decoding; performing a thirddetermination of whether to deactivate a communication interfaceconfigured to process a received signal based on a result of the seconddetermination; receiving beamforming information about whether abeamforming characteristic applied to the previous TTI is same as abeamforming characteristic applied to the current TTI from atransmitter; and requesting the transmitter to transmit a controlchannel demodulation reference signal (DMRS) mapped to resourcesthroughout an entire band, wherein the beamforming information isprovided to the receiver from the transmitter through radio resourcecontrol (RRC) signaling or downlink control information (DCI)transmission, wherein the first determination comprises: checkingwhether resource mapping of a control channel DMRS of the previous TTIis same as resource mapping of a control channel DMRS of the currentTTI; and determining whether to reuse the control channel information ofthe previous TTI based on the beamforming information and a result ofthe checking, wherein the checking is performed based on whether thecontrol channel DMRS of the previous TTI and the control channel DMRS ofthe current TTI are mapped to resources throughout the entire band, andwherein, based on the beamforming characteristic applied to the previousTTI being same as the beamforming characteristic applied to the currentTTI and the resource mapping of the control channel DMRS of the previousTTI being same as the resource mapping of the control channel DMRS ofthe current TTI, whether to reuse the control channel information of theprevious TTI is determined based on whether channel characteristicmaintenance time has ended.
 8. The wireless communication method ofclaim 7, wherein based on determining that the channel characteristicmaintenance time has not ended, the control channel information of theprevious TTI is reused to decode the control channel of the current TTI.9. The wireless communication method of claim 7, wherein, based ondetermining that the channel characteristic maintenance time has ended,different control channel information which is different from thecontrol channel information of the previous TTI is used to decode thecontrol channel of the current TTI without reusing the control channelinformation of the previous TTI.
 10. A wireless communication method ofa receiver, the wireless communication method comprising: performing afirst determination of whether to decode a control channel of a currenttransmission time interval (TTI) based on control channel information ofa previous TTI; decoding the control channel of the current TTI based ona result of the first determination; performing a second determinationof whether a data channel is included in the current TTI based on aresult of the decoding; and performing a third determination of whetherto deactivate a communication interface configured to process a receivedsignal based on a result of the second determination, wherein based onthe second determination indicating that the data channel is included inthe current TTI, the third determination comprises: maintaining thecommunication interface in an activated state, performing a fourthdetermination of whether to decode the data channel based on datachannel information of the previous TTI, and decoding the data channelbased on a result of the fourth determination, wherein the fourthdetermination comprises: checking whether a channel characteristicmaintenance time has ended; and determining whether to reuse the datachannel information of the previous TTI based on a result of thechecking, and wherein, based on the result of the checking indicatingthat the channel characteristic maintenance time has ended, differentdata channel information which is different from the data channelinformation of the previous TTI is used to decode the data channel ofthe current TTI without reusing the data channel information of theprevious TTI.
 11. The wireless communication method of claim 10,wherein, based on the current TTI being a TTI immediately following anend of the channel characteristic maintenance time, the different datachannel information comprises newly obtained data channel information ofthe current TTI.
 12. The wireless communication method of claim 10,wherein, based on the current TTI not being a TTI immediately followingan end of the channel characteristic maintenance time, a type of thedifferent data channel information is determined based on whether achannel characteristic is maintained between the current TTI and animmediately previous TTI of the current TTI.
 13. The wirelesscommunication method of claim 12, wherein whether the channelcharacteristic is maintained between the current TTI and the immediatelyprevious TTI is determined based on a correlation between a channelestimation value of the immediately previous TTI and a channelestimation value of the current TTI or a Doppler spread estimation valueof the immediately previous TTI.
 14. The wireless communication methodof claim 13, wherein based on the correlation between the channelestimation value of the immediately previous TTI and the channelestimation value of the current TTI indicating that the channelcharacteristic is maintained between the current TTI and the immediatelyprevious TTI: the different data channel information comprises newlyobtained data channel information of the current TTI, the channelcharacteristic maintenance time is restarted with respect to animmediately following TTI of the current TTI, and data channels of aplurality of TTIs including the immediately following TTI within thechannel characteristic maintenance time are decoded based on the newlyobtained data channel information of the current TTI.
 15. The wirelesscommunication method of claim 13, wherein, based on the correlationbetween the channel estimation value of the immediately previous TTI andthe channel estimation value of the current TTI indicating that thechannel characteristic between the current TTI and the immediatelyprevious TTI is not maintained, the different data channel informationcomprises newly obtained data channel information of the current TTI,and wherein the wireless communication method further comprises:determining whether the channel characteristic is maintained between thecurrent TTI and an immediately following TTI of the current TTI based ona correlation between the channel estimation value of the current TTIand a channel estimation value of the immediately following TTI.
 16. Thewireless communication method of claim 13, wherein, based on the Dopplerspread estimation value of the immediately previous TTI indicating thatthe channel characteristic is maintained between the current TTI and theimmediately previous TTI: the different data channel informationcomprises data channel information obtained from the immediatelyprevious TTI, the channel characteristic maintenance time is restartedwith respect to the current TTI, and data channels of a plurality ofTTIs including the current TTI within the channel characteristicmaintenance time are decoded based on the data channel informationobtained from the immediately previous TTI.
 17. The wirelesscommunication method of claim 13, wherein, based on the Doppler spreadestimation value of the immediately previous TTI indicating that thechannel characteristic is not maintained between the current TTI and theimmediately previous TTI, the different data channel informationcomprises newly obtained data channel information of the current TTI,and wherein the wireless communication method further comprises:determining whether the channel characteristic is maintained between thecurrent TTI and an immediately following TTI of the current TTI based ona Doppler spread estimation value of the current TTI.